Add hooks to enable and disable Relay GC to RelayFBEnvironment
Add hooks to enable and disable Relay GC to RelayFBEnvironment

Reviewed By: kassens

Differential Revision: D6339572

fbshipit-source-id: 17e1d6da65052577b00c6057cc816ae1ffa92f56

iamchenxin/relay,cpojer/relay,iamchenxin/relay,cpojer/relay,dbslone/relay,freiksenet/relay,facebook/relay,facebook/relay,wincent/relay,kassens/relay,josephsavona/relay,wincent/relay,kassens/relay,zpao/relay,facebook/relay,wincent/relay,yungsters/relay,iamchenxin/relay,facebook/relay,voideanvalue/relay,xuorig/relay,freiksenet/relay,wincent/relay,yungsters/relay,wincent/relay,freiksenet/relay,kassens/relay,josephsavona/relay,kassens/relay,benjaminogles/relay,benjaminogles/relay,apalm/relay,xuorig/relay,voideanvalue/relay,benjaminogles/relay,facebook/relay,atxwebs/relay,iamchenxin/relay,atxwebs/relay,kassens/relay,xuorig/relay,atxwebs/relay,kassens/relay,cpojer/relay,facebook/relay,cpojer/relay,voideanvalue/relay,apalm/relay,apalm/relay,atxwebs/relay,voideanvalue/relay,zpao/relay,zpao/relay,yungsters/relay,voideanvalue/relay,xuorig/relay,wincent/relay,xuorig/relay,voideanvalue/relay,xuorig/relay,dbslone/relay,josephsavona/relay